Mechanical component having at least one fluid transport circuit and method for designing same in strata

ABSTRACT

A mechanical part useful in various fields of application including plastic and metal processing is produced using a computer-aided design process including a preliminary break-down of the body of the part into elementary strata, followed by manufacture of the elementary strata, and reconstruction of the part. During break-down of the part, at least one fluid transport circuit, which is designed and modeled beforehand, is broken down into elementary chambers ( 20 ) in accordance with the break-down of the part. The elementary chambers are produced in the elementary strata ( 7   i ) forming the part during manufacture of the strata, and the fluid transport circuit is reconstructed during superposition and assembly of the strata.

BACKGROUND OF THE INVENTION

The present invention relates to a mechanical part that includes atleast one circuit for containing a fluid, and to a method for producingsuch a part.

The present invention is applicable to a broad range of fields such as,for example, mechanical engineering (for example, for the manufacture ofcylinder heads), printing (for the production of ink-marking circuits),or other fields. In addition, the present invention preferably, but notexclusively, applies to the field of plastics processing, and moreparticularly, to the problems posed by the thermal regulation of moldingtools (dies or punches).

The thermal regulation of an injection molding tool has the function ofextracting thermal energy provided by the molten thermoplastic to theoutside of the tool. Such energy is imparted to the thermoplastic by theplasticating screw to allow the thermoplastic to conform to theimpression being made. Such energy must then be removed from thethermoplastic so the part can be ejected (without any “distortion” ofthe molding impression). Such extraction takes place under conditionsdefined beforehand, during the design of the part and of the tool.

The solution most commonly used to carry out the function of cooling andregulating molding tools is to produce a series of channels in the bodyof the tool, through which a heat-transfer fluid can circulate. Thenature of the fluid depends on the desired average temperature in thetool.

To obtain optimally effective regulating channels, it is necessary forthe channels to be able to form a layer facing the part, or whichexactly follow the shape of the part, and for such channels to beseparated from the part by as thin a wall as possible. In practice, thissolution could not be achieved, both for technical reasons and becauseof the high mechanical stresses generated by the injection moldingprocess.

A similar solution is sometimes obtained by a system of channels havinga square cross section, and that approximately follow the shape of thepart. This solution is used in special cases and is known to be usedonly on simple geometrical shapes (mainly on cylindrical punches). Sucha solution gives rise to the problem of sealing between the attachedparts, resulting in substantial delays and manufacturing costs.

Such channels are most often produced by drilling, which is the leasteffective but simplest solution. Since the holes can be drilled only ina straight line, an entire series of drilling operations is necessary inorder to follow the impression as closely as, possible. The circuit isthen formed by using fluid-tight plugs, or even by using externalbridging arrangements for difficult cases, which are best avoided to theextent possible due to the risk that the resulting circuits can becrushed or broken while the mold is being handled.

Insufficient cooling can result either due to geometrical precisionproblems or excessively long cycle times. In the worst cases, this cancause production shutdowns, during which the mold is left open to beregulated by natural convection.

Despite all of these risks of malfunction, this aspect of the tool isoften neglected when designing molds for injection molding. Theregulating system is very often designed as the last item, and must beplaced between the various ejectors, the guiding column, etc. This hasbeen found to be erroneous because this function is the keystone of theinjection molding process. The conditions for cooling the part play anessential role in the level of internal stresses in the injection-moldedparts and in the crystallinity of the polymer, and therefore, in theaging stability and the mechanical properties of the parts.Consequently, production of the cooling/regulating channels currentlyrepresents a major challenge in improving performance in plasticsprocessing.

One solution which has been proposed is disclosed in an article in thejournal “Emballages Magazine” entitled “How to Optimize the Molding ofPlastics” (January-February 2002, supplement No. 605). The disclosedsolution entails the production of a first, prototype mold, the behaviorof which is observed and recorded during cooling. A computer thenanalyzes the data and deduces the dimensions and the positions of pinsintended to improve heat exchange. This method leads to the constructionof a second mold which is more effective than the first mold, and whichincludes a set of pins placed in accordance with a design established bythe computer. Such a solution is time-consuming and requires priorexperimentation.

Another solution which has been proposed is disclosed in InternationalPublication No. WO 02/22341. The disclosed solution places a tubularinsert provided with radially disposed pins inside a parison, in orderto increase the heat exchange. The application of this solution islimited, and complicated to implement.

The object of the present invention is to alleviate the aforementioneddrawbacks of the prior art and to provide an entirely novel method fordesigning and manufacturing the tool and its fluid transport circuit.

SUMMARY OF THE INVENTION

In accordance with the present invention, the tool and its fluidtransport circuit are designed and manufactured in a fully optimizedmanner, and in accordance with the requirements of the part to beproduced, using the process known by the trademark “STRATOCONCEPTION”which is disclosed in European Patent No. 0 585 502, and improvements ofwhich are disclosed in French Patent Publications No. FR 2,789,188, FR2,789,187, FR 2,808,896, FR 2,809,040 and in French Patent ApplicationNo. FR 02/80514, the contents of which are fully incorporated byreference as if fully set forth herein.

In general, the “STRATOCONCEPTION” process relates to a method forproducing a mechanical part based on a computer-aided design. In apreliminary step, the body of the part is broken down into elementarystrata. The elementary strata are then manufactured, followed byreconstruction of the part in its entirety by superposing and assemblingthe manufactured strata.

During break-down of the part, at least one fluid transport circuit isbroken down into elementary chambers in accordance with the break-downassociated with that of the part. The fluid transport circuit isdesigned and modeled beforehand, and the elementary chambers areproduced in the elementary strata of the part during manufacture of thestrata. The fluid transport circuit is then reconstructed, in itsentirety, during superposition and assembly of the strata.

As an alternative, and during break-down of the part, an additionalisolating circuit can be broken down into elementary isolating chambersin accordance with the break-down associated with that of the part. Theelementary isolating chambers are produced in the elementary strata ofthe part during manufacture of the strata. The isolating circuit is thenreconstructed during superposition and assembly of the set of strata.

Further in accordance with the present invention, a mechanical part isprovided which is comprised of a body with at least one fluid transportcircuit. The fluid transport circuit is, for example, comprised ofchannels produced in the body and at a predetermined distance from aheat exchange surface. The circuit is produced by the above-describedmethods, and is reconstructed in its entirety during assembly of thestrata, based on a succession of elementary chambers that are broughtinto communication in a fluid-tight manner and that are provided in atleast one portion of the strata. The fluid transport circuit ispreferably filled with a fluid selected from the group of fluidsincluding a heat exchange fluid, a thermal insulation fluid, a liquid orpulverulent material, and a marking fluid.

In some embodiments, and after reconstruction, the circuit forms a setof channels in the body of the part which are preferably parallel andwhich follow or copy a molding surface at a predetermined distance fromthe molding surface. In other embodiments, and after reconstruction, thecircuit forms a layer-shaped chamber in the body of the part. Thecircuit preferably includes a connection to a regulating device.

As a further alternative, the part can further include an additionalisolating circuit, which is also reconstructed in its entirety duringassembly of the strata. The additional isolating circuit is based on asuccession of elementary chambers that are brought into communication ina fluid-tight manner, and are provided in at least one portion of thestrata.

Further description of the present invention is given below, withreference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional view of a mold with prior art coolingchannels.

FIG. 1 a is a vertical section of the mold of FIG. 1.

FIGS. 2 a and 2 b illustrate the principle of breaking down the mold ofFIG. 1 a into unitary cells.

FIG. 3 is a three-dimensional view of a mold which has been stratified,in accordance with the present invention, and which includesfollower-axis channels for the circulation of a regulating fluid thatfollows the shape of the molding surface.

FIGS. 3 a and 3 b are vertical sections of the mold of FIG. 3, and itsbreak-down into unitary cells.

FIG. 4 is a three-dimensional view of a mold which has been stratified,in accordance with the present invention, and which includesfollower-surface channels for fluid circulation.

FIGS. 4 a and 4 b are vertical sections of the mold of FIG. 4, and itsbreak-down into unitary cells.

FIG. 5 is a three-dimensional view of a mold which has been stratified,in accordance with the present invention, and which includes a followerlayer for the circulation of a regulating fluid which follows or copiesthe shape of the molding surface.

FIG. 5 a is a vertical section of the mold of FIG. 5.

FIG. 6 is a nonlimiting representation of the follower layer.

FIGS. 7 a and 7 b are representations of two successive strata definingthe follower layer of FIG. 6.

FIG. 8 is a partial, nonlimiting representation of a stratum thatincludes fins for producing a laminar effect in the follower layer.

FIG. 9 is a partial, nonlimiting representation of a stratum thatincludes fins for producing a turbulent effect in the follower layer.

FIG. 10 is a representation of a unitary thermal cell of a regulatingfollower layer.

FIG. 11 is a schematic section of a mold which has been stratified inaccordance with the present invention, and which includes isolatingfollower channels.

FIG. 12 is a schematic section of a mold which has been stratified inaccordance with the present invention, and which includes an isolatingfollower layer.

FIG. 13 is a diagram of a method of filling the isolating layer orchannels.

FIG. 14 is a diagram of a dynamic regulating device in accordance withthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows the conventional principle of cooling a mold (1). Severalregulating channels (2) are produced by drilling and/or by the use ofplugs, to form a three-dimensional network of regulating channels (2).The regulating channels (2) are parallel to the molding surface (3) ofthe mold (1), which is shown in FIG. 1 a, after the molding tool hasbeen manufactured. The regulating channels (2) are placed at locationsthat are generally defined empirically by the mold designer.

FIGS. 2 a and 2 b schematically show the basic concept of the presentinvention. In accordance with the present invention, and to make iteasier to space the channels and to determine their dimensions, theregion of the mold which surrounds the molding surface (3) which will bein contact with the material to be molded and which will consequently besubjected to heating and cooling stresses during production of the part,is broken down into elementary cells (4) over a given thickness. Forease of understanding, FIGS. 2 a and 2 b schematically show such abreak-down into unitary thermal cells for the conventional mold shown inFIG. 1. The break-down shown in FIGS. 2 a and 2 b is only one of thebreak-downs that can be employed to facilitate the determination of thedimensions of the channels.

In accordance with the present inventive concept, each cell isdetermined so that the cell is traversed by at most one regulatingchannel. The positions and the dimensions of the channels which arethereafter calculated will depend on the thermal stresses that theaffected region of the mold will have to undergo during the variousoperations for producing the part (molding, blowing, cooling, demolding,etc.).

The foregoing inventive concept for designing and producing optimizedregulating channels is performed using the “STRATOCONCEPTION” processpreviously referred to. The design of the channels derives from priormodeling, in terms of unitary thermal cells, but this is not to be takenas limiting. As an example, a unitary cell (22) (see FIG. 10) is formed,over a given thickness, from a part of the mold (22′) in contact on oneof its faces with the polymer to be cooled, from a part of this polymer(33), and from a unitary chamber (15) in which the fluid circulates.

FIGS. 3, 3 a and 3 b show a first application of the foregoing basicprinciples to a stratified mold produced using the “STRATOCONCEPTION”process (or one of its improvements). In this application, the mold (1)is produced using software that breaks the mold down into elementarystrata (7). The strata (7) are produced by micromilling a plate. Thestrata (7) are then joined together by superposing the strata so thatone of the inter-stratum planes of the stratum (7 _(i)) is appliedagainst one of the inter-stratum planes of the next stratum (7 ₁₊₁).

In accordance with the present invention, each stratum in regions of themold concerned with heat exchange is calculated to include a regulatingchannel (2) that emerges in one of the inter-stratum planes (either theupper plane of a stratum or the lower plane of a stratum). Therequirements of the part, for example, the cycle time, thecharacteristics of the material, etc., will dictate the dimensions ofthe channels (2). The channels are dimensioned or designed beforehand,according to the requirements of the application, and are produced bymicromilling during production of the strata. The channels (2) are thenreconstructed in their entirety upon assembly of the strata.

The embodiment shown in FIGS. 3 a and 3 b includes at least one channel(2) of square cross-section in the stratum, or in the strata (7) of themold region in question. The channel has a plane bottom (8) parallel tothe inter-stratum plane, and two side walls (9, 10) perpendicular to theinter-stratum plane (5 or 6) from which the channel (2) emerges. Such anembodiment is referred to as a “follower axis” embodiment because thelongitudinal axis (11) of the channel is located at a predetermineddistance (d) from the molding surface (3). Such an embodiment makes iteasier to cut the channel (2) in a stratum (7) of the series (7 _(i),with i from 1 to n), by laser or by water-jet micromilling. Providing across-section with a square or rectangular base also improves the heatexchange compared with a circular cross-section.

The embodiment shown in FIGS. 4, 4 a and 4 b includes a channel (2), atleast one of the side walls (13, 14) of which is shaped to reproduce orcopy a portion of the molding surface (3). Such an embodiment isreferred to as a “follower surface” embodiment because all the points onthe follower side wall (for example, the wall (14) shown) are located ata distance (d′) from the molding surface (3), with the bottom (12) andthe other side wall (13) remaining parallel, or optionally,perpendicular, respectively, to the inter-stratum plane (5 or 6).

For the embodiments shown in FIGS. 3 a to 4 b, the channels are producedby turning the strata over and by providing the channels with a depthless than the thickness of one stratum. It is to be understood that suchembodiments are nonlimiting examples, and that the channels can haveother shapes, and a depth greater than the thickness of one stratum.

The corners between the walls and the bottom of the channels are“broken” to limit stress concentrations. The channels follow the moldingsurface at a predetermined depth (d′) that is constant, or that varies,depending on the region to be cooled or the cooling requirements.

The position of a channel in the interface plane of a stratum (7 _(i))is calculated so that, when the strata (7 _(i)) are being stacked, thechannel is blocked by the interface plane of the next stratum (7_(i+1)), so that there is no overlap between the two emerging channels.The size and cross-section of the channels is calculated according tothe amount of heat to be removed.

In another embodiment of the present invention, shown in FIGS. 5 and 6,the mold (1) includes a fluid circulation layer (15) that follows orcopies the shape of the molding surface. This follower layer has apredetermined thickness and is bounded by a surface (16) facing themolding surface (3) and a surface (17) facing toward the outside of themold. The follower layer is predetermined so that all points of thesurface (16) facing the molding surface are at a predetermined distanceor depth (D) from the molding surface (3), which is why this circulationlayer has been called a follower layer. The distance (D) is constant, orcan vary, depending on the region to be cooled or the thermal stresses.Such a fluid layer constitutes a true, continuous thermal barriersurrounding the part to be produced. The follower layer (15) has beenexemplified by a solidified fluid, which is shown in isolation in FIG.6, with a feed header (18) for inflow of the regulating fluid and afluid outlet header (19).

As in the previous illustrative examples, the mold is produced by a“STRATOCONCEPTION” process. In each stratum which is involved in theheat exchange, a portion of the circuit, which will be referred to as an“elementary chamber” (20), is produced during the micromilling step, andthe circuit is then formed in its entirety after all of the strata havebeen superposed.

The two strata (7 _(i)) and (7 _(i+1)) of the mold that surround ordefine the chamber for circulating the fluid of the follower layer ofFIG. 6 have been shown in FIGS. 7 a and 7 b. Such a fluid layerconstitutes a true, continuous thermal barrier surrounding the part tobe produced. The corners between the faces and the bottom of the chamberare also broken, to limit stress concentrations and head losses.

A multiplicity of transverse fins (21) can further be provided insidethe chamber, for mechanical reinforcement between the two walls and forstirring the fluid. The fins can be of various shapes depending on theapplication and the desired effects, for example, a laminar effect (seeFIG. 8) or a turbulent effect (see FIG. 9). The shape, size andcross-section of the fins depend on the amount of heat to be removed andon the requirements due, for example, to the mechanical stresses (joinradius between the fins and the faces of the layer, etc.).

The follower layer (15) can be broken down into unitary heat exchangecells (22) for the purpose of mathematically modeling all of the heatexchanges undergone or transmitted by the mold during the production ofa part. A unitary exchange cell (22) is individually illustrated in FIG.10 and is shown diagrammatically on one of the strata (7 _(i+1)) in FIG.7 b. The various characteristic parameters of the virtual base cell (22)are used, in accordance with the present invention, for mathematicallycalculating in optimum manner the dimensions of the part and of thecircuit before they are produced. This is done, using techniques whichare otherwise known, by writing heat balance equations using analyticalmodels and/or multiphysical numerical simulations.

Two further embodiments are shown in FIGS. 11 and 12, which operate tolimit the thermal conduction toward the sides of the mold (convectivelosses with the outside) and/or toward the bottom of the mold(conductive losses with the machine frame). These molds include,respectively, a plurality of isolating follower channels (23) (FIG. 11),and parallel to the isolating follower channels (23), an isolatingfollower layer (24) (FIG. 12). Such embodiments can also be producedduring the micromilling step of the “STRATOCONCEPTION” process, and canbe designed in the same way as the regulating follower channels (2) orthe regulating follower layer (15).

The isolating channels (23) and the isolating layer (24) are located ata constant, or at a variable distance from the regulating follower layer(15), and are located on the outside of the follower layer (15), placingthem between the follower layer (15) and the outside of the mold (theside and bottom faces). The dimensions and the cross-sections of theisolating channels (23) and the isolating layer (24) depend on theisolation to be provided, and are also obtained from multiphysicalnumerical simulations. For example, the isolating channels (23) and theisolating layer (24) are thicker when they are close to the machineplatens than when they are close to the external faces, since the lossesby conduction into the platens are greater than the losses by naturalconvection relative to the external faces. The isolating channels andlayers form either an active isolation, or secondary regulation, or apassive isolation if they are filled with an insulating material.

FIG. 13 schematically shows a method of filling a mold with aninsulating resin (25) in a vacuum chamber (26), for achieving passiveisolation. A volume of resin (25) is introduced under an air vacuum intothe internal volume. The volume of resin (25) is greater by a fewpercent (owing to shrinkage) than the internal volume of the channels orthe layer to be filled. A telltale (27) is used to ensure completefilling.

FIG. 14 shows an example of an active thermal regulating device foroperating on the regulating fluid circulating in a follower layer (15)which is externally isolated by an isolating layer (24). The coolingfluid (28), at a temperature (T₁), is sent by a pump (29) into thechamber (20) of the follower layer (15). If necessary, a solenoid valve(30) controlled by a regulator (31) mixes a colder liquid (32) at atemperature (T₂) with the cooling liquid (28). Such mixing will dependon the measured difference between a temperature (T₃) measured in themold region lying between the molding surface (3) and a referencetemperature (T₄) chosen for the regulation being performed.

Moreover, to obtain a molding tool suitable for withstanding themechanical stresses to be encountered, a mechanical brace can beprovided during the bonding of the strata. This includes an applicationof mechanical adhesive on the regions extending from the channels, asfar as the outside of the mold, and an application of adhesive with apredetermined thermal conductivity on the regions extending from thecooling circuits, as far as the molding surface. The term “coolingcircuit” is to be understood to mean both the network of channels andthe layer construction.

In general, the method of the present invention ensures that the strataare held in place in a technically and economically suitable manner forthe intended application by the choice of a technique for assembling thestrata, namely, adhesive bonding, brazing, screwing or the like.

The method of the present invention makes it possible to causeregulation of the tools to comply with the requirements of the parts tobe produced, allowing very fine regulation in the case ofhigh-performance parts, or active regulation in the case of consumerparts. This serves to optimize regulation of the tools, to improve theproductivity of the tools, to optimize the mechanical strength of theparts being produced, to reduce geometrical distortion, to reduceinternal stresses due to cooling, to reduce the internal stresses due tofilling, to reduce thermal inertia of the tools, and to reduce theirweight.

Furthermore, it is possible to produce bulk or crude items (preformed orotherwise) dedicated to a part, with the optimized system of channelsalready produced. Each stratum is seen as an independent solid. As aconsequence, one is concerned only with the heat supplied to thestratum, and the channel is dimensioned in this way.

Hotspots can, therefore, be treated with greater care. Any imbalances incooling, due to the mold/material contact conditions and/or difficultiesof gaining access between the die and the punch, can be eliminated.

At any point in the impression, heat removal is optimized. It ispossible to achieve uniform cooling (in terms of flux, temperature, heattransfer coefficient) over the entire surface of the part, while stillensuring a cooling time which is adjusted to the shortest possible, orminimum cooling time, and while nevertheless limiting the residualstresses and deformations in the part.

Due to the low inertia of the mold, it is possible to control thecooling dynamically. Consequently, it is possible to heat the mold,after ejection of the part, to keep the mold hot until the end of thefilling operation, and to then cool the mold. Mold cooling is startedslightly before the end of a filling, depending on the reaction time ofthe tool itself (a very short time due to the reduced inertia of suchtools). By improving the filling operation, its duration is shortened,making it easier for the polymer to flow. The level of internal stressesin the injection-molded part is also reduced.

The combination of optimized cooling with dynamic control of the thermalregulation of the mold allows the cycle time to be reduced by decreasingthe filling time and the cooling time. This combination also allows theinternal stresses in the injection-molded parts to be considerablyreduced, which reduces distortion and post-shrinkage of the parts, andwhich increases the dimensional quality and improves the aging behaviorof the parts. Irrespective of the type of cooling desired, thedimensional, structural and mechanical qualities of the injection-moldedparts are improved, whether the parts are high-performance products,attractive products or consumer products.

Heat transfer is optimized by cell modeling, charts and the simulationsused to choose each regulating parameter. The positioning and thedimensions of the fins influence the heat transfer, the mechanicalstrength of the tools, and the control of turbulence (header losses,etc.). Such positioning must, therefore, be studied and optimized usingnumerical simulation and optimization tools.

The design of the feed headers (18) and the outlet headers (19) is keyfor regulating fluid flow control. This design is also simulated andnumerically optimized (for example, with reference to FIG. 6, byproviding wider or more numerous nozzles (34) at the necessary points).

The time needed to bring the tools into service (to temperature) isshortened. The weight of such tools is also reduced.

The mold has a low thermal inertia due to thermal and mechanicaloptimization of the wall thickness between the follower layer and themolding surface. The thermal inertia of the mold can also be increasedby the isolating action of the second layer, if necessary. As a result,the volume to be regulated is optimal. Minimal inertia gives the tools agreater production capacity. This is because the regulating time is notonly optimized, but the tool returns more rapidly to its initialconditions in order to start a new cycle.

Of course, the examples and/or applications described above do not limitthe scope of the present invention.

In particular, the present invention extends to many other known fieldsof application, namely metal foundry work, the building industry, theprinting industry or others. Depending on requirements, the fluid chosencan be a liquid, a gas or a powder, and can be used, for example, forpurposes of heat exchange, for isolation, for marking, for pluggingand/or for assembly and/or rigidification by solidification (or otherprocesses, etc.).

Moreover, and for the sake of simplification and clarity, while theabove-described break-down operations have been performed in parallelplanes, this is in no way limiting, and such operations can also beperformed in warped surfaces. It should also be mentioned thatbreak-down of the circuit or circuits is tied to that of the part, inthe sense that this can be identical, or tied by a mathematicalrelationship.

Finally, while the term “cell” has been used with various qualifiers,the term intellectually denotes the same concept.

1. A method for producing a mold by computer-aided design including apreliminary step in which body portions of the mold are broken down intoelementary strata, followed by steps including manufacture of theelementary strata to form manufactured strata and reconstruction of themold by superposing and assembling the manufactured strata, wherein themethod comprises the steps of: defining a fluid transport circuit in themold; breaking down the fluid transport circuit into a plurality ofelementary chambers as part of the break-down of the mold and during thebreak-down of the mold; producing the elementary chambers in themanufactured strata during the manufacture of the manufactured strata;and completely reconstructing the fluid transport circuit during thesuperposition and the assembly of the manufactured strata; breaking downan isolating circuit coupled with the fluid transport circuit into aplurality of elementary isolating chambers as part of the break-down ofthe mold and during the break-down of the mold; producing the elementaryisolating chambers in the manufactured strata during the manufacture ofthe manufactured strata, simultaneously producing the elementarychambers and the elementary isolating chambers during the manufacture ofthe manufactured strata; reconstructing the isolating circuit during thesuperposition and the assembly of the manufactured strata, wherein theelementary isolating chambers are placed in fluid-tight communication,simultaneously producing the fluid transport circuit and the isolatingcircuit; and combining the elementary isolating chambers of theisolating circuit to form a thermal barrier between the fluid transportcircuit and side and bottom portions of the mold.
 2. The method of claim1 wherein the elementary chambers are produced in the manufacturedstrata before the manufactured strata are reconstructed to form thefluid transport circuit.
 3. The method of claim 1 which further includesthe step of combining the elementary chambers of the fluid transportcircuit to form a cooling circuit in the body of the mold.
 4. The methodof claim 3 which further includes the step of combining the elementarychambers of the fluid transport circuit to form a three-dimensionalnetwork of channels in the body of the mold.
 5. The method of claim 3which further includes the step of combining the elementary chambers ofthe fluid transport circuit to form a layer-shaped chamber in the bodyof the mold.
 6. The method of claim 1 wherein the step of producing theelementary chambers in the manufactured strata further includes the stepof forming the elementary chambers in surface portions of themanufactured strata, to a depth which is less than a defined thicknessof the manufactured strata.
 7. The method of claim 6 which furtherincludes the step of combining the elementary chambers of the fluidtransport circuit with surface portions of adjacent manufactured strata,to form the fluid transport circuit.
 8. The method of claim 1 whichfurther includes the step of forming the thermal barrier as a continuousthermal barrier.
 9. The method of claim 8 which further includes thestep of combining the elementary isolating chambers of the isolatingcircuit to form a network of follower channels in the body of the mold.10. The method of claim 8 which further includes the step of combiningthe elementary isolating chambers of the isolating circuit to form alayer-shaped chamber in the body of the mold.
 11. The method of claim 1which further includes the step of uniformly spacing the isolatingcircuit from the fluid transport circuit.
 12. The method of claim 1which further includes the step of providing the isolating circuit witha uniform thickness.